As an ambulance vibration-proof rack, there has been known, for example, one disclosed in Patent Document 1 proposed by the present applicant. This includes a swingable upper frame provided to lower frames via a link mechanism and swings up and down and back and forth by a vibration transmitted when an ambulance is travelling, owing to a repulsive force of first permanent magnets which are attached to the lower frames and the upper frame, with their repulsive magnetic poles facing each other. On the other hand, when the sick or wounded placed on a stretcher is given a predetermined treatment such as a cardiac massage, a vibration-proof rack needs to be locked so as not to move, but in the type swinging up and down and back and forth as disclosed in Patent Document 1, the easy locking has been difficult. In view of this point, as disclosed in Patent Document 2, the present applicant has proposed a mechanism for easily and quickly locking the ambulance vibration-proof rack which swings up and down and back and forth as disclosed in Patent Document 1.